The techniques used in the manufacture of integrated circuits, transistors, and the like require that the quality of doping liquids used in their manufacture be carefully controlled. Particularly, the inclusion of fine particle contaminants into the doping liquid must be prevented, since such an inclusion has a direct influence on the yield of the products. For this reason, the liquid is usually precisely filtered, and clean containers are filled with the filtered liquid in a purified environment (i.e., a clean room). The containers generally employed are 1 to 8-liter glass bottles.
The operation of opening and filling the glass bottles with the doping liquid is carried out in a clean room. Although some incorporation of dust, contaminents, and the like into the doping liquid is inevitable, the amount is not as great as would be present if the filling were done outside the clean room. A further disadvantage to the use of glass bottles is that the containers are liable to break in the course of transport and distribution and disposal of the used empty containers is also burdensome because the are not reusable.
As far as the users of the doping liquid are concerned, it is also troublesome to open the glass bottle and transfer the doping liquid therein into another container for use in the manufacturing device because during the transfer dust and other contaminants may get into the contents of the bottle. In extreme cases, the contents may spill or overflow.
In view of such inconveniences, the inventors of the present application developed a returnable can, i.e., a receiving container for the doping liquid, which could be easily connected to a pipe which leads to the doping liquid treatment process without opening the returnable can and without transferring the liquid therein into another container each time it is used.
This receiving container is constructed so that the doping liquid therein may be fed to a semiconductor-manufacturing device by utilizing gas pressure, as disclosed in Japanese Patent Provisional Publication No. 21021/1984.
FIGS. 1-3 attached hereto are prior art devices showing the receiving container and an arrangement by which the receiving container is connected to the semiconductor-manufacturing device.
As shown in FIG. 1, a canister 10 which is a returnable can including doping liquid 20 is composed of a liquid receiving container body 13 and a flange 14, which is provided with a coupler 11 for allowing the liquid to be transported therethrough and a male coupler 12 for allowing a gas to pass therethrough. In FIG. 2, these couplers 11, 12 are protected by caps 30 and 31, respectively.
In the case where the returnable can is connected to a semiconductor-manufacturing device 1, a purified nitrogen gas is fed to the canister 10 through couplers 17, 12, and the drug liquid 20 is delivered to the device 1 through the couplers 16, 11 by virtue of the nitrogen gas pressure, as exhibited in FIG. 3.
Such a returnable can may receive a greater amount of the doping liquid than a conventional glass bottle, however, the volume of the doping liquid cannot be monitored, depending on the material used for the returnable can. Further, since a larger amount of the doping liquid is contained therein, it is difficult to always monitor its remaining volume and exchange the depleted bottle for a new one at the proper time, and if a worker is not conscious of the liquid's absence in the bottle and if the doping liquid treatment device continues to operate, untreated inferior goods will be manufactured. Even if a metering instrument is mounted to the semiconductor-manufacturing device, for detecting a decrease in the volume of the liquid, such as an integrating flowmeter, it will be exceedingly difficult to quickly exchange the empty returnable can for a new one.